It is common in the nursery business to use greenhouses for germinating and growing plants.
Typically, plants are planted as seeds or cuttings in 11 by 22 inch plastic flats or in pots. Pots are typically 3, 4, or 5 inches in diameter but may be anywhere from 2 to 10 inches in diameter. The plants may be kept in the original flats or pots until sold or, after reaching a certain size, may be transplanted to larger pots to provide sufficient soil volume to support the plant's root system and keep it from getting root bound. If a large plant is desired, several transplantings into larger pots may be appropriate to continually provide the proper soil volume to support the plant. As the plant grows, its foliage takes up a continually larger space, making it necessary to spread individual pots or flats apart to allow sufficient sunlight to reach the foliage. Growing plants in greenhouses therefore requires frequent movement of plants from one location to another, such as from the potting shed to the germinating greenhouse, and from one area of a particular greenhouse to another to accommodate sunlight demands of the growing foliage.
A majority of greenhouses employ benches to provide a platform for laying out plants and keep the stock elevated above the floor. Benches are typically constructed of steel, wood, plastic, or concrete frames with galvanized expanded metal, turkey wire, or special bench fabrics spread across the top. Galvanized expanded metal or other bench surfaces allow water to drain from the plants during frequent watering.
A bench is typically 3.5 to 7 feet wide by as long as needed. The bench surfaces are 16 to 36 inches above ground level to bring them to a comfortable work level for personnel. Most frequently, benches do not have a rim around the outer perimeter of the top surface. For those that do have a rim, it is frequently a fairly short lip.
As it costs a great deal of money to heat a large volume of air, space is at a premium in greenhouses. A bench would typically be 60 to 100 feet long or even longer. As many rows of benches as possible are fitted in each greenhouse to maximize the growing space available to plants and the aisles between the rows of benches are typically kept very narrow, usually from 16 to 20 inches wide. These narrow aisles make it difficult to transport potted plants or flats during the many times they are rotated within a greenhouse or from one greenhouse to another. A main aisle, measuring 8 to 12 feet wide, may be created within the greenhouse to allow carts or an overhead track system access to the ends of the benches in the greenhouse.
Methods currently used by greenhouses to transfer plants include the use of portable conveyors. The conveyors are typically in multiple sections with each section being ten to twelve feet long. One section, the drive section, is motorized and quite heavy. The other conveyor sections connect to the drive section through a gear mechanism at each junction. The main unit, the drive section, is quite heavy and becomes quite awkward to move around. The other conveyor sections, typically constructed of aluminum, are not very heavy but are still awkward to move down the benches. It requires two persons to hook the conveyor sections together and the maximum practical conveying distance with one drive unit is about 80 feet.
The conveyor is typically configured with all its sections in place and sections are removed and the conveyor shortened as the benches are filled with plants. The conveyor is typically laid on top of a bench near one aisle and two benches are therefore filled with plants as subsequent sections of the conveyor are removed.
The type of time and effort required to lay out and connect the sections of the conveyor and then remove sections as the benches are filled in the type of effort most greenhouse operators have found does not pay. Most greenhouses have found that it is easier and more efficient to just let people carry the flats or potted plants. One person can typically carry only one or two flats at a time, and perhaps four to eight pots at a time, depending on the size of the pots. Therefore there is typically a lot of labor involved in moving plants around in a greenhouse, and multiple trips must be made up and down the aisles to distribute the plants on the benches.
Greenhouse operators have automated the filling process of the pots or flats; they've automated the movement of the plants through the main aisles of the greenhouses, which can be quite a distance at times, by the use of carts or overhead conveyors. However, the time consuming portion of moving plants around greenhouses which involves the movement of the plants onto, off of, and around the benches themselves, because of the narrow aisles and the large expanse that would be required to install a mechanized conveyor system, have prevented full automation.
Accordingly, the present art has not proven fully satisfactory in providing an arrangement has not proven fully conveying flats or potted plants within greenhouses.